Director / Principal Researcher yujung@kaeri.re.krHe developed a millimeter-wave free-electron laser (FEL) in 1995 and a compact terahertz FEL in 2000. He won the International FEL Prize at the International FEL Conference of 2013 for his contribution to the FEL field. Recently, he is dedicated to develope a ultrafast electron diffraction facility which has the best temporal accuracy in the world (~tens femtoseconds) and use it for ultrafast science.